Shedding Light on Vitamin D Status and Its Complexities During Pregnancy, Infancy and Childhood: an Australian Perspective
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International Journal of Environmental Research and Public Health Perspective Shedding Light on Vitamin D Status and Its Complexities during Pregnancy, Infancy and Childhood: An Australian Perspective Nelfio Di Marco 1, Jonathan Kaufman 1,2 and Christine P. Rodda 1,2,3,* 1 Women’s and Children’s Division, Sunshine Hospital, St Albans, VIC 3021, Australia; nelfi[email protected] (N.D.M.); [email protected] (J.K.) 2 Department of Paediatrics, University of Melbourne, Royal Children’s Hospital, Parkville, VIC 3052, Australia 3 Australian Institute for Musculoskeletal Science, University of Melbourne, Sunshine Hospital, St Albans, VIC 3021, Australia * Correspondence: [email protected] Received: 10 January 2019; Accepted: 7 February 2019; Published: 13 February 2019 Abstract: Ensuring that the entire Australian population is Vitamin D sufficient is challenging, given the wide range of latitudes spanned by the country, its multicultural population and highly urbanised lifestyle of the majority of its population. Specific issues related to the unique aspects of vitamin D metabolism during pregnancy and infancy further complicate how best to develop a universally safe and effective public health policy to ensure vitamin D adequacy for all. Furthermore, as Australia is considered a “sunny country”, it does not yet have a national vitamin D food supplementation policy. Rickets remains very uncommon in Australian infants and children, however it has been recognised for decades that infants of newly arrived immigrants remain particularly at risk. Yet vitamin D deficiency rickets is entirely preventable, with the caveat that when rickets occurs in the absence of preexisting risk factors and/or is poorly responsive to adequate treatment, consideration needs to be given to genetic forms of rickets. Keywords: Vitamin D deficiency; rickets; vitamin D during pregnancy; foetal life; infancy and lactation; UV B; sun exposure; health literacy; mineral ion nutrition; vitamin D dependent rickets 1. Introduction In the 1950s and 1960s, during the post-World War Two economic boom in Australia, rickets was considered a disease of the past in Australia, and in the global setting, a disease of poverty. During this era, the typical Australian lifestyle was characterised by active outdoor living, with many mothers able to stay at home with their children. A seemingly trivial lifestyle practice was that most household laundry was hung out to dry outside on most days on the back yard rotary clothes hoist, an unrecognised opportunity for regular sun exposure, before the advent of widespread use of clothes driers. 1.1. Traditional Practices for Prevention and Treatment of Rickets Rickets was essentially first described contemporaneously by Daniel Whistler in a dissertation from the University of Leiden in 1645 and five years later by Cambridge Physician Dr Francis Glisson [1], who systematically described and published his personal observations [2,3]. Based on his observations from clinical examination and post-mortem findings, Glisson concluded that this condition was neither congenital nor contagious, but was essentially due to environmental factors. Int. J. Environ. Res. Public Health 2019, 16, 538; doi:10.3390/ijerph16040538 www.mdpi.com/journal/ijerph Int. J. Environ. Res. Public Health 2019, 16, 538 2 of 17 Furthermore, he had also accurately noted that rickets was rarely observed before six months of age and was predominantly a disease of infants and toddlers [3]. However, it took nearly another 300 years to elucidate the scientific underpinning of Glisson’s observations. 1.1.1. Cod Liver Oil The medicinal use of cod liver oil dates back to the 1700s [4]. Among people living in coastal areas, there was a long-standing appreciation in folklore of the medicinal benefit of cod liver oil, but the earliest recorded medicinal use of cod liver oil dates to 1789, is credited to Dr Darbey of the Manchester Infirmary [4], for his treatment of rheumatism. The recognition of cod liver oil as a specific remedy against rickets was noted as early as 1824 in the German medical literature. In 1861, Trousseau of France opined that rickets was caused by lack of sun exposure and a faulty diet, and that cod liver oil could effectively cure it [4]. Although it was clear to the medical and scientific community in the late 1800s that cod liver oil and sunlight exposure could cure rickets, it took until the early 1900s for researchers to discover that Vitamin D deficiency was the underlying cause of so called “nutritional” rickets. Although similar in fatty acid composition to other fish oils, cod liver oil has higher concentrations of vitamins A and D. According to the United States Department of Agriculture, a tablespoon (13.6 g or 14.8 mL) of cod liver oil contains 4080 µg of retinol (vitamin A) [5] and 34 µg (1360 iu) of vitamin D [6]. The Dietary Reference Intake of vitamin A is 900 µg per day for adult men and 700 µg per day for adult women, while that for vitamin D is 5 µg (200 iu)–15 µg (600 iu) per day (doses increase with advancing years). The tolerable adult Upper Intake levels (ULs) are 3000 µg/day (vitamin A) and 100 µg (4000 iu)/day Vitamin D. The recommended daily intake of Vitamin A (as retinol equivalent) is 300–400 µg for infants and toddlers, 600–900 µg for male adolescents and 600–700 µ for female adolescents [5,6]. Whilst acknowledging that cod liver oil appropriately administered successfully prevented vitamin D deficiency rickets in the past, there is also a substantial risk of vitamin A intoxication without careful administration and its use to prevent vitamin D deficiency rickets can no longer be recommended. 1.1.2. “Sunning” Heliotherapy, or sunlight therapy has been used for centuries therapeutically and dates back to ancient Roman and Greek times [7]. In the first half of the 19th century sunlight was believed to have a role in the treatment of jaundice as well as in the treatment of rickets [7]. Placing a child in a room with sunlight exposure, for ten minutes at a time was commonplace [7,8], however this practice would have been ineffective in the prevention of rickets, as UVB is not transmitted through glass [9]. It has also been established that “sunning” babies for the purposes of jaundice treatment is not appropriate and is potentially harmful. Phototherapy administered under medical monitoring is required to treat neonatal jaundice. In 1890, addressing the aetiology of rickets, Palm studied the relationship between the incidence of rickets and its geographical distribution, and concluded that rickets was caused by lack of exposure to sunlight. Palm also observed that despite a superior diet and relatively better sanitary conditions, infants residing in Britain were more at risk for rickets than those living in the tropics [2,3]. Exposure to plenty of sunshine, which was the norm for infants residing in the tropics, he proposed, was responsible for their protection against rickets. Palm recommended the “systematic use of sun-baths as a preventive and therapeutic measure in rickets” [3]. As skin cancer rates climbed steeply from the 1940s, the scientific and medical communities began to understand the potentially damaging effects of sun exposure to skin [2]. Although research has shown overwhelmingly that sunlight exposure is linked to skin cancer, ongoing “sunning” practices are still practised throughout the world [7,8,10]. Aladag and colleagues [7] found that although families and parents were aware of the benefits of sunlight exposure, there was a poor understanding of Int. J. Environ. Res. Public Health 2019, 16, 538 3 of 17 potential dangers and concerns around sunlight exposure. In general families were found to be “sunning” their babies for bone health, jaundice, nappy rash and to increase vitamin D. In geographical locations where health literacy and access to health care is low, “sunning” practices continue, likely to be related to the passing down of these practices throughout the generations. 2. A Resurgence of Rickets in Australia In 1972 Mayne and McCredie reported a resurgence of rickets in Melbourne, recognising newly arrived southern European migrants and premature infants as the predominant risk group [11]. These authors reviewed radiological cases of rickets from 1961–1971 at the Melbourne Royal Children’s Hospital, and identified 59 cases of vitamin D deficiency rickets, and these comprised just over half the cases of radiological rickets identified. In the 1960’s vitamin D assays were not available [12] in public hospital settings in Melbourne, and the diagnosis was a clinical one, based on radiological findings without features of other underlying chronic conditions associated with rickets. The Victorian State Government had established an infant welfare program for all Victorian infants and toddlers, under the directorship of Dr Vera Scantlebury-Brown in 1926. Under her leadership infant morbidity and mortality decreased dramatically [13]. Anecdotal evidence suggests that the use of cod liver oil to prevent rickets was also recommended around this time. However, most of the infants and toddlers described by Mayne and McCredie came from poor migrant families who did not attend maternal child health programs and furthermore had limited sun exposure. Although the need for vitamin D supplementation in premature infants is now well recognised [14,15], other environmental and lifestyle issues leading to vitamin D deficiency rickets were not considered a public health concern at the time. The authors’ abstract concluded with “A plea is made for adequate instruction of our migrant population in the prevention of this disease” [11]. Over the past 30 years there have been dramatic demographic and lifestyle changes which have had a major impact on the vitamin D status of the Australian population. Thankfully the White Australia Policy, which prevented migration of darker skinned people throughout most of the 20th century, was finally abolished in 1973.